1. Field of the Invention
The present invention relates generally to a system and method for assigning a mobile IP (Internet Protocol), and in particular, to a system and method for assigning a mobile IP to a mobile node.
2. Description of the Related Art
In general, a mobile node (MN) is used for a voice (circuit) call or a data service for its mobility. Further, due to its mobility, the mobile node is not limited to a single location. Therefore, a user of the mobile node can be provided with a data service, such as a mobile Internet service, even while moving from place to place.
Recently, active research has been carried out on a system and method for providing stable services. In order to provide a stable data service to the mobile node while securing the mobility, it is necessary to assign a mobile IP to the mobile node. To this end, a method for assigning a mobile IP to the mobile node is in development.
FIG. 1 illustrates a network configuration for assigning a mobile IP to a mobile node. A network configuration and a location registration process for assigning a mobile IP to a mobile node will be described with reference to FIG. 1. A mobile node (MN) 10 transmits a location registration request signal to a foreign agent (FA) 20, in an initialization process after power on or upon receipt of a location registration request signal. However, since the MN 10 has the mobility as stated above, the MN 10, although it is registered in a Korea-based service provider, transmits the location registration request signal even in a non-registered country, for example, the United States. If a service agreement has been made between the mobile communication service providers, the location registration request is available. A detailed description of this will be given with reference to FIG. 1.
The MN 10 wirelessly sends a location registration request signal to the FA 20. The FA 20 can detect an address of a home agent (HA) 30 included in the location registration request signal received from the MN 10. Thus, the FA 20 performs location registration on the MN 10 in reply to the location registration request signal from the MN 10. The FA 20 transmits a location registration request signal for the MN 10 to the HA 30 through a network 25, along with an address of the FA 20. The HA 30 then stores the address of the FA 20 where the MN 10 is located. That is, the HA 30 stores COA (Care-of-Address) of the FA 20 to which the MN 10 belongs. Thereafter, the HA 30 sends a location registration reply signal to the FA 20 in response to the location registration request signal received from the MN 10 through the FA 20. Through this process, the location registration is performed on the MN 10. The location of the MN 10 must be registered in the HA 30, in order that the MN 10 might receive data from a correspondent node (CN) 40. A description of the communication performed in the network will be made with reference to FIG. 2.
FIG. 2 illustrates a network configuration for assigning a mobile IP to a mobile node. A description will be made of a process for exchanging data between the CN 40 and the MN 10 in the case when the location of the MN 10 has been registered in the HA 30 through the process of FIG. 1. A network 25a between the FA 20 and the HA 30, a network 25b between the HA 30 and the CN 40 and a network 25c between the FA 20 and the CN 40 can be identical to or different from one another. Herein, the networks will be assumed to be an IP network.
The CN 40 is a computer for transmitting data to an Internet server or the MN 10. To transmit data to the MN 10, the CN 40 sends the data to the HA 30 through the IP network 25b. The HA 30 stores therein the address of the FA 20 where the MN 10 is located, then reads the address of the FA 20 and sends the data to the FA 20 through the IP network 25a. The FA 20 then transmits the data to the MN 10. The data transmitted to the MN 10 includes an address of the CN 40. To transmit data to the CN 40, the MN 10 sends data to the FA 20. The FA 20 then transmits the data directly to the CN 40 without passing through the path of the FA20→the HA 30→the CN 40. This is because the MN 10 sends a data transmission request using a destination address. Therefore, the data transmission path is different from the data reception path.
Recently, as Internet service is used worldwide at a low service rate, communication networks tend to accommodate Internet service. Further, active research has been carried out on a private network capable of accommodating Internet service. Based upon this research, a study is being made on a virtual private network (VPN) in which service is not limited in location, and a method for assigning a mobile IP even in a non-registered area.
The private network can be divided into a dedicated WAN (Wide Area Network) and a dial network. The dedicated WAN connects one site to another site with a permanent line, while the dial network, such as a PSTN (Public Switched Telephone Network), connects a line through dialing when necessary.
A configuration of a network to which a VPN is connected through a router based on the IP, and a data exchanging process will be described with reference to FIG. 3. In FIG. 3, an IP backbone is connected to routers, and in particular, ISP (Internet Service Provider) routers 120, 130 and 140 become edge routers to be connected to CPE (Customer Promise Equipment) routers 150, 160 and 170. IP tunnels are formed among the ISP routers 120, 130 and 140 in the IP network 100, to exchange data. In addition, stub links are formed between the ISP routers and the CPE routers. As occasion demands, a backup link is formed between CPE router 160 and the ISP router 120, the routers existing in different locations, and a backdoor link is formed between the CPE routers 150 and 170. Through the network configuration, the Internet service is provided and a voice call is performed.
However, since the network shown in FIG. 3 is not interlinked with the network shown in FIG. 2, the MN 10 cannot be provided with the stable service. That is, when the MN 10 is registered in the VPN, it cannot be simultaneously applied to the VPN and the mobile communication network while maintaining its mobility. In other words, it is not easy to combine the network of FIG. 2 for performing the mobile service of the mobile communication network with a network of FIG. 3 for performing the IP service. In addition, although the networks are combined with each other, since the MN 10 has the mobility, it passes through different IP routers each time it moves. Therefore, the CPE routers must be modified, making it difficult to assign a mobile IP to the MN 10. That is, although the MN 10 is simultaneously applied to the above-stated two networks, it is not possible to assign the mobile IP to the MN 10 to perform the Internet service.